Abstract: A method and apparatus are provided for non-contact optical flow measurement in a pipe, the apparatus having one or more modules configured to sense light that is scattered off several points longitudinally along a wall of a pipe having a medium flowing therein and to provide a signal containing information about a deflection of the wall of the pipe that can be used to determine a parameter related to the medium flowing in the pipe, including a flow rate of the medium. The deflection in the pipe wall is caused by a turbulence induced pressure fluctuation which in turn induces a localized pipe wall deflection.